Fix errors

public/index.html

@@ -166,7 +166,7 @@ Get the _position_ of an element which satisfies a certain condition.
 ```rust
 let v = vec![1, 2, 3, 4, 5];
 
-v.iter().position(|&x| x == 3); // Some(1)
+v.iter().position(|&x| x == 3); // Some(2)
 v.iter().position(|&x| x == 0); // None
 ```
 
@@ -356,7 +356,7 @@ Look at the next element without advancing.
 
 ```rust
 let v = vec![1, 2, 3, 4, 5];
-let mut iter = v.iter();
+let mut iter = v.iter().peekable();
 
 iter.peek(); // Some(&&1)
 iter.next(); // Some(&1)